Heart valve prosthesis

ABSTRACT

Mitral valve prosthesis are disclosed that include a frame or support structure having an inflow portion, a valve-retaining tubular portion and a pair of support arms. The inflow portion radially extends from a first end of the valve-retaining tubular portion and the pair of support arms are circumferentially spaced apart and radially extend from an opposing second end of the valve-retaining tubular portion. The inflow portion is formed from a plurality of struts that outwardly extend from the first end of the valve-retaining tubular portion with adjacent struts of the plurality of struts being joined, wherein each strut of the plurality of struts has a substantially s-shaped profile and at least one twisted area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Appl. No. 61/895,106, filedOct. 24, 2013, which is incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present invention is directed to heart valve prosthesis, and moreparticularly to a mitral valve prosthesis for use in a transcathetermitral valve replacement procedure.

BACKGROUND OF THE INVENTION

A human heart includes four heart valves that determine the pathway ofblood flow through the heart: the mitral valve, the tricuspid valve, theaortic valve, and the pulmonary valve. The mitral and tricuspid valvesare atrioventricular valves, which are between the atria and theventricles, while the aortic and pulmonary valves are semilunar valves,which are in the arteries leaving the heart. Ideally, native leaflets ofa heart valve move apart from each other when the valve is in an openposition, and meet or “coapt” when the valve is in a closed position.Problems that may develop with valves include stenosis in which a valvedoes not open properly, and/or insufficiency or regurgitation in which avalve does not close properly. Stenosis and insufficiency may occurconcomitantly in the same valve. The effects of valvular dysfunctionvary, with regurgitation or backflow typically having relatively severephysiological consequences to the patient.

Recently, prosthetic valves supported by stent structures that can bedelivered percutaneously using a catheter-based delivery system havebeen developed for heart and venous valve replacement. These prostheticvalves may include either self-expanding or balloon-expandable stentstructures with valve leaflets attached to the interior of the stentstructure. The prosthetic valve can be reduced in diameter, by crimpingonto a balloon catheter or by being contained within a sheath componentof a delivery catheter, and advanced through the venous or arterialvasculature. Once the prosthetic valve is positioned at the treatmentsite, for instance within an incompetent native valve, the stentstructure may be expanded to hold the prosthetic valve firmly in place.One example of a stented prosthetic valve is disclosed in U.S. Pat. No.5,957,949 to Leonhardt et al., which is incorporated by reference hereinin its entirety.

Although transcatheter delivery methods may provide safer and lessinvasive methods for replacing a defective native heart valve,preventing leakage between the implanted prosthetic valve and thesurrounding native tissue remains a challenge. Leakage sometimes occursdue to the fact that minimally invasive and percutaneous replacement ofcardiac valves typically does not involve actual physical removal of thediseased or injured heart valve. Rather, the replacement stentedprosthetic valve is delivered in a compressed condition to the valvesite and expanded to its operational state within the diseased heartvalve, which may not allow complete conformance of the stent framewithin the native heart valve and can be a source of paravalvularleakage (PVL). As well PVL may occur after a heart valve prosthesis isimplanted due to movement and/or migration of the prosthesis that canoccur during the cardiac cycle. Movement due to changes in chordaltensioning during the cardiac cycle may be particularly problematic formitral valve prosthesis, as chordal tensioning can axially unseat, liftor rock the prosthesis within or into the atrium resulting in PVL.Accordingly, there is a continued need to provide mitral valveprosthesis having structure that maintains sealing within the nativeanatomy during the cardiac cycle.

BRIEF SUMMARY OF THE INVENTION

Mitral valve prosthesis according to embodiments hereof includes a framehaving a flexible, anatomically conforming inflow portion that isdesigned to maintain sealing with the atrial surface surrounding thenative mitral valve during the cardiac cycle. The frame or supportstructure defines an inflow portion, a valve-retaining tubular portionand a pair of support arms. The inflow portion radially extends from afirst end of the valve-retaining tubular portion and the pair of supportarms are circumferentially spaced apart and radially extend from anopposing second end of the valve-retaining tubular portion. The inflowportion is formed from a plurality of struts that outwardly extend fromthe first end of the valve-retaining tubular portion with adjacentstruts of the plurality of struts being, wherein each strut of theplurality of struts has a substantially s-shaped profile and at leastone twisted area.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of embodiments thereof asillustrated in the accompanying drawings. The accompanying drawings,which are incorporated herein and form a part of the specification,further serve to explain the principles of the invention and to enable aperson skilled in the pertinent art to make and use the invention. Thedrawings are not to scale.

FIG. 1 is a perspective sectional view of a heart that depicts a mitralvalve and various structural features related thereto.

FIG. 1A is a superior view of the mitral valve shown in FIG. 1 isolatedfrom the surrounding heart structure.

FIG. 2 is a side view of a mitral valve prosthesis in accordance with anembodiment hereof shown in a deployed configuration.

FIG. 2A is a top view of an inflow area of the mitral valve prosthesisof FIG. 2 taken in the direction of line A-A therein.

FIG. 3 is a side view of a frame of the mitral valve prosthesis of FIG.2.

FIG. 3A is a top or inflow view of the frame of FIG. 3 taken in thedirection of line A-A therein.

FIG. 3B is a cross-sectional view of a strut of the frame of FIG. 3Ataken along line B-B therein.

FIG. 4 is a side view of the frame of FIG. 3 rotated 90° about alongitudinal axis L_(A) thereof from the orientation shown in FIG. 3.

FIG. 4A is a side sectional view of the frame of FIG. 4 taken along lineA-A therein that highlights the s-shape feature of the inflow section ofthe frame.

FIG. 4B is a cross-sectional view of a strut of the frame of FIG. 4Ataken along line B-B therein.

FIG. 5 depicts a patterned tube for forming the frame of FIGS. 3, 3A, 4and 4A laid flat for illustrative purposes.

FIG. 5A is a cross-sectional view of the patterned tube of FIG. 5 takenalong line A-A therein.

FIG. 6 is a photograph of an inflow area of a frame in accordance withthe embodiment of FIGS. 3, 3A, 4 and 4A.

FIG. 6A is an enlarged view of an encircled area A of FIG. 6.

FIG. 7 is a photograph of a side of a frame in accordance with theembodiment of FIGS. 3, 3A, 4 and 4A.

FIG. 8 is a photograph of a side of a frame in accordance with anotherembodiment hereof.

FIG. 8A is a photograph of an inflow area of the frame of FIG. 8 takenin the direction of line A-A therein.

FIG. 8B is a cross-sectional view of a strut of the frame of FIG. 8taken along line B-B therein.

FIG. 9 depicts a patterned tube for forming the frame of FIGS. 8 and 8Alaid flat for illustrative purposes.

FIG. 9A is a cross-sectional view of the patterned tube of FIG. 9 takenalong line A-A therein.

FIG. 10 is a photographic image of an implanted mitral valve prosthesisin accordance with an embodiment hereof.

FIG. 11 shows an inflow portion of the frame of FIGS. 8 and 8A afterimplantation.

FIG. 12 shows the post-implantation inflow portion of the frame shown inFIG. 11 transposed on a pre-implantation inflow portion of the frame asshown in FIG. 8A.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described withreference to the figures, wherein like reference numbers indicateidentical or functionally similar elements. The terms “distal” and“proximal” are used in the following description with respect to aposition or direction relative to the treating clinician. “Distal” or“distally” are a position distant from or in a direction away from theclinician. “Proximal” and “proximally” are a position near or in adirection toward the clinician. In addition, as used herein, the terms“outward” or “outwardly” refer to a position radially away from alongitudinal axis of a frame of the prosthesis and the terms “inward” or“inwardly” refer to a position radially toward a longitudinal axis ofthe frame of the prosthesis. As well the terms “backward” or“backwardly” refer to the relative transition from a downstream positionto an upstream position.

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Although the description of embodiments hereof are in thecontext of treatment of heart valves and particularly a mitral valve,the invention may also be adapted for use in other valve replacementprocedures where it is deemed useful. Furthermore, there is no intentionto be bound by any expressed or implied theory presented in thepreceding technical field, background, brief summary or the followingdetailed description.

FIG. 1 is a perspective sectional view of a heart (H) that depicts amitral valve (MV) and various structural features related thereto, withFIG. 1A being a superior view of the mitral valve isolated fromsurrounding heart structure. The mitral valve is found between the leftatrium (not shown) and the left ventricle (LV) and is surrounded by andattached to a fibrous atrioventricular ring of the heart that may bemore commonly referred to as the mitral valve annulus (MVA). As bestshown in FIG. 1A, the mitral valve annulus may be considered to have aD-shape rather than being circular or elliptical. The mitral valveincludes anterior and posterior leaflets (AL, PL) that open duringdiastole to allow blood flow from the left atrium to the left ventricle.During ventricular systole, the anterior and posterior leaflets close toprevent backflow to the left atrium while the mitral valve annuluscontracts and reduces its surface area to help provide complete closureof the leaflets. The anterior and posterior leaflets are attached topapillary muscles (PM) within the left ventricle by way of the chordaetendinae (CT), which are strong, fibrous strings or structures attachedto the leaflets of the heart on the ventricular side. When the anteriorand posterior leaflets of the mitral valve close, the chordae tendinaeare tensioned to prevent the leaflets from swinging back into the atriumcavity.

Due to the unique shape of a native mitral valve and the functionalityof the structure associated therewith that can cause axial movement of aprosthetic mitral valve during the cardiac cycle, i.e., axial movementthat may be caused by the cyclic tensioning of the chordae tendinaeand/or contraction of the D-shaped mitral valve annulus duringventricular systole, a mitral valve prosthesis according to embodimentshereof includes a frame having a flexible, anatomically conforminginflow portion that is designed to maintain sealing with the atrialsurface surrounding the mitral valve during the cardiac cycle.

FIG. 2 is a side view of a mitral valve prosthesis 200 in accordancewith an embodiment hereof shown in a deployed configuration, with FIG.2A being a top view of an inflow area of prosthesis 200 taken in thedirection of line A-A in FIG. 2. Prosthesis 200 includes a valvecomponent 220 attached within an interior of a frame or supportstructure 210. Valve component 220 is a one-way bicuspid replacementvalve having first and second valve leaflets 224A, 224B. In anotherembodiment, valve component 220 may be a one-way tricuspid replacementvalve having three valve leaflets. Valve leaflets 224A, 224B are suturedor otherwise securely and sealingly attached to an interior surface offrame 210 and/or to graft material 226, which encloses or lines variousportions of frame 210. In embodiments in accordance herewith, graftmaterial 226 secured to frame 210 within an inflow area of prosthesis200 aids in sealing and graft material 226 secured to frame 210proximate an outflow area of prosthesis 200 provides a tent-like orhammock structure 228, which functions to reduce or eliminateinteraction between frame 210 and the chordae tendinae when prosthesis200 is implanted within a native mitral valve.

FIGS. 3, 3A, 4 and 4A illustrate frame 210 in a deployed configurationremoved from a remainder of prosthesis 200. FIGS. 3 and 4 are side viewsof frame 210, with FIG. 4 showing frame 210 rotated 90° about alongitudinal axis L_(A) thereof from the orientation shown in FIG. 3.FIG. 3A is a top or inflow view of frame 210 taken in the direction ofline A-A in FIG. 3 and FIG. 3B is a cross-sectional view of a strut 512Bof frame 210 taken along line B-B in FIG. 3A. FIG. 4A is a sectionalview of frame 210 taken along line A-A in FIG. 4 and FIG. 4B is across-sectional view of strut 512B of frame 210 taken along line B-B inFIG. 4A.

Frame 210 is a unitary structure that defines an inflow portion 202, avalve-retaining tubular portion 204 and a pair of support arms 206A,206B. In the deployed configuration of frame 210, inflow portion 202outwardly extends from a first or inflow end 203 of valve-retainingtubular portion 204 and support arms 206A, 206B backwardly extend fromcircumferentially spaced apart locations of an opposing second oroutflow end 205 of valve-retaining tubular portion 204. When prosthesis200 is implanted within a native mitral valve, inflow portion 202 offrame 210 is configured to engage an area of the left atrium thatsurrounds the native mitral valve, valve-retaining tubular portion 204of frame 210 is configured to axially extend through the native mitralvalve and thusly situates valve component 220 within the mitral valveannulus, and support arms 206A, 206B are configured to capturerespective valve leaflets of the mitral valve and to secure them withinthe left ventricle without obstructing the outflow area of prosthesis200 or the left ventricular outflow tract.

Frame 210 is a unitary structure, as previously noted above. In aninitial step in manufacturing frame 210, a tube 510 of a suitablematerial is etched, cut or otherwise machined to have the patterndepicted in FIG. 5. FIG. 5 depicts for illustrative purposes onlypatterned tube 510 laid flat so that the cut structures of inflowportion 202, valve-retaining tubular portion 204 and support arms 206A,206B may be more readily identified and described. Valve-retainingtubular portion 204 has a stent-like framework that definesdiamond-shaped openings 518 and a series of upstream valleys 514A anddownstream valleys 514B. Support arms 206A, 206B are formed from innerand outer looped struts 513, 515 with the outer looped struts 515extending from spaced apart valleys 514B of valve-retaining tubularportion 204 and with the inner looped struts 513 extending from spacedapart downstream peaks 517 of valve-retaining tubular portion 204.

Inflow portion 202 is formed from a plurality of struts 512 having a cutwidth W_(C) that is less than a thickness T thereof, as shown in FIG. 5Awhich is a cross-sectional view of strut 512B taken along line A-A inFIG. 5. Each strut 512 defines a base segment 509 and divergent firstand second branch segments 511A, 511B. Accordingly, strut 512 may beconsidered to have a Y-shaped cut pattern. Base segments 509 of arespective pair of struts 512, for instance base segments 509A, 509B ofstruts 512A, 512B, extend from every other valley 514 at inflow end 203of valve-retaining tubular portion 204. A plurality of crowns 513 areformed between first and second branch segments 511A, 511B of adjacentstruts 512. Crowns 513 form radially outward ends of inflow portion 202of frame 210, as shown in FIG. 3A. Circumferentially adjacent crowns 513are not directly connected to each other and thereby provide inflowportion 202 with improved flexibility.

Subsequent processing steps are performed on patterned tube 510 in orderto form frame 210 as shown in FIGS. 3, 3A, 4 and 4A. In one or moreprocessing steps, patterned tube 510 is radially expanded to set atubular shape and diameter of valve-retaining tubular portion 204 thatis suitable for receiving valve component 220 therein. In one or moreadditional processing steps, support arms 206A, 206B are rotated outwardand backward relative to outflow end 205 of valve-retaining tubularportion 204 and heat treated to set a shape thereof. In one or moreadditional processing steps, struts 512 of inflow portion 202 ofpatterned tube 510 are made to outwardly extend from inflow end 203 ofvalve-retaining tubular portion 204 and subjected to a forming processto have a substantially s-shaped profile, as best seen in FIG. 4A. In anembodiment and somewhat counter-intuitively, a first bend 416A and anopposing second bend 416B that form the substantially s-shaped profileof strut 512 are bent or curved over the cut width W_(C) of the strut,as shown in FIGS. 3B and 4B, rather than being bent or curved overthickness T of the strut. First and second bends 416A, 416B of s-shapedstrut 512 are able to be formed in this manner due to one or moretwisted areas TA₁, TA₂, TA₃ of strut 512 that occur during formation ofinflow portion 202. More particularly with reference to FIGS. 3A and 4A,base segment 509 of each strut 512 has a twisted area TA₁ near oradjacent to where the respective base segment 509 outwardly extends frominflow end 203 of valve-retaining tubular portion 204. Although notintending to be bound by theory, twisted area TA₁ turns cut width W_(C)of the respective strut 512 approximately 90 degrees from the cutpattern shown in FIG. 5 such that the narrower portion Wc of therespective strut 512 is subjected to the forming process that createsfirst and second bends 416A, 416B. As well with reference to FIG. 3A,first and second branch segments 511A, 511B of each strut 512 havetwisted areas TA₂, TA₃, respectively, near or adjacent to theirrespective crowns 513. Although not intending to be bound by theory,twisted areas TA₂, TA₃ turn cut width W_(C) of the respective strut 512in a direction opposite of twisted area TA₁ to return cut width W_(C) toa similar orientation as shown in the cut pattern in FIG. 5, whichresults in cut width Wc facing inward and outward along at least aportion of first and second branch segments 511A, 511B of struts 512 andthrough crowns 513 of inflow portion 202.

In the embodiment of frame 210 shown in FIGS. 3, 3A, 4 and 4A, inflowportion 202 may be described as having a ring of alternating openings orcells C1, C2 that are formed between respective portions of struts 512and crowns 513. Cells C1, C2 have widths W₁, W₂, respectively, withwidth W₁ of cell C1 being less than width W₂ of cell C2, as best shownin FIG. 3A. Although not intending to be bound by theory, thealternating size of cells C1, C2 contributes to base segments 509 thatemanate from a common valley 514 of tubular portion 204 having twistedareas TA₁ that twist or turn away from each other, or in other wordstwist in opposite directions from each other. For example with referencethe pair of base segments 509A, 509B shown in FIGS. 3A, 6 and 6A,twisted area TA₁ of base segment 509A will turn strut 512Acounterclockwise toward its adjacent cell C2, such that twisted area TA₁of base segment 509A may be considered to have a left-hand twist, andtwisted area TA₁ of base segment 509B will turn strut 512B clockwisetoward its adjacent cell C2, such that twisted area TA₁ of base segment509B may be considered to have a right-hand twist.

The s-shaped struts 512 that form inflow portion 202 of frame 210 actsimilarly to cantilever beams when interacting with the anatomy of theheart as a supporting and sealing structure of prosthesis 200. Duringthe pressure changes and cyclical contractions of the heart, thes-shaped struts 512 are able to deflect while maintaining an axial forceagainst the atrial surface of the heart that is sufficient for sealingand the prevention of paravalvular leakage between the frame and tissuesurface. As well the combination of twisted areas TA₁, TA₂, TA₃ ands-shape of struts 512 of inflow portion 202 permit the inflow area ofprosthesis 200 to readily deflect, flex and/or move during the cardiaccycle while also maintaining sufficient axial stiffness to providesealing contact with the atrial surface that surrounds the implantedprosthesis. In addition, the twisted areas TA₁, TA₂, TA₃ of s-shapedstruts 512 may reduce strain and improve the structural integrity offrame 210, and more particularly the structural integrity of inflowportion 202 thereof.

FIGS. 8 and 8A illustrate a frame 810 in a deployed configuration inaccordance with another embodiment hereof that is suitable for use informing a mitral valve prosthesis similar to prosthesis 200 describedabove. FIG. 8 is a side view of frame 810, with FIG. 8A being a top orinflow view of frame 810 taken in the direction of line A-A in FIG. 8.Frame 810 is a unitary structure that defines an inflow portion 802, avalve-retaining tubular portion 804 and a pair of support arms 806A,806B. In the deployed configuration of frame 810, inflow portion 802outwardly extends from a first or inflow end 803 of valve-retainingtubular portion 804 and support arms 806A, 806B backwardly extend fromcircumferentially spaced apart locations of an opposing second oroutflow end 805 of valve-retaining tubular portion 804. When implantedwithin a native mitral valve as a support structure of a mitral valveprosthesis, inflow portion 802 is configured to engage an area of theleft atrium that surrounds the native mitral valve, valve-retainingtubular portion 804 is configured to axially extend through the nativemitral valve and thusly situates a prosthetic valve component within themitral valve annulus, and support arms 806A, 806B are configured tocapture respective valve leaflets of the mitral valve and to secure themwithin the left ventricle without obstructing the outflow area of theprosthetic valve or the left ventricular outflow tract.

In an initial step in manufacturing frame 810, a tube 910 of a suitablematerial is etched, cut or otherwise machined to have the patterndepicted in FIG. 9. FIG. 9 depicts for illustrative purposes onlypatterned tube 910 laid flat so that the cut structures of inflowportion 802, valve-retaining tubular portion 804 and support arms 806A,806B may be more readily identified and described. Valve-retainingtubular portion 804 has a stent-like framework that definesdiamond-shaped openings 918 and a series of upstream valleys 914A anddownstream valleys 914B. Each support arm 806A, 806B is formed to haveinner side struts 913A, 913B and an outer looped strut 915. Outer loopedstruts 915 extend from spaced apart downstream peaks 917B ofvalve-retaining tubular portion 804 and inner side struts 913A, 913Bextend from respective downstream valleys 914B within their respectiveouter looped strut 915 and connect therewith at opposing interiorlocations 919A, 919B. In another embodiment in accordance herewith, tube910 may be cut into a pattern such that frame 810 is formed to havesupport arms 206A, 206B as described with reference to the previousembodiment.

Inflow portion 802 is formed from a plurality of struts 912 having a cutwidth W_(C) that is less than a thickness T thereof, as shown in FIG. 9Awhich is a cross-sectional view of a strut 912 taken along line A-A inFIG. 9. Each strut 912 defines a base segment 909 and first and secondbranch segments 911A, 911B, which diverge from base segment 909 at arespective node 921. Accordingly, strut 912 may be considered to have aY-shaped cut pattern. A base segment 909 of a respective strut 912extends from every upstream valley 914A at inflow end 803 ofvalve-retaining tubular portion 804. Each base segment 909 has a lengththat disposes a respective node 921 of strut 912 upstream of upstreampeaks 917A. In an embodiment, base segment 909 has a length such thatnode 921 of strut 912 is disposed upstream of upstream peaks 917A by atleast half a length of the base segment. Crowns 913 are formed betweenfirst and second branch segments 911A, 911B of adjacent struts 912.Crowns 913 form radially outward ends of inflow portion 902 of frame910, as shown in FIG. 8A. Circumferentially adjacent crowns 913 are notdirectly connected to each other and thereby provide inflow portion 802with improved flexibility.

Subsequent processing steps are performed on patterned tube 910 in orderto form frame 810 as shown in FIGS. 8 and 8A. In one or more processingsteps, patterned tube 910 is radially expanded to set a tubular shapeand diameter of valve-retaining tubular portion 804 that is suitable forreceiving a prosthetic valve component therein. In one or moreadditional processing steps, support arms 806A, 806B are rotated outwardand backward relative to outflow end 805 of valve-retaining tubularportion 804 and heat treated to set a shape thereof. In one or moreadditional processing steps, struts 912 of inflow portion 802 ofpatterned tube 910 are made to outwardly extend from inflow end 803 ofvalve-retaining tubular portion 804 and subjected to a forming processto have a substantially s-shaped profile, as best seen in FIG. 8.Somewhat counter-intuitively, a first bend 816A and an opposing secondbend 816B that form the substantially s-shaped profile of strut 912 arebent or curved over the cut width W_(C) of the strut, as shown in FIG.8B, rather than being bent or curved over thickness T of the strut.First and second bends 816A, 816B of s-shaped strut 912 are able to beformed in this manner due to one or more twisted areas TA₁, TA₂, TA₃ ofstrut 912 that occur during formation of inflow portion 802. Moreparticularly with reference to FIG. 8A, base segment 909 of each strut912 has a twisted area TA₁ near or adjacent to where the respective basesegment 909 outwardly extends from inflow end 803 of valve-retainingtubular portion 804. Although not intending to be bound by theory,twisted area TA₁ turns cut width W_(C) of the respective strut 912approximately 90 degrees from the cut pattern shown in FIG. 9 such thatthe wider thickness T of the respective strut 912 is subjected to theforming process that creates first and second bends 816A, 816B. As wellwith reference to FIG. 8A, first and second branch segments 911A, 911Bof each strut 912 have twisted areas TA₂, TA₃, respectively, near oradjacent to their respective crowns 913. Although not intending to bebound by theory, twisted areas TA₂, TA₃ turn cut width Wc of therespective strut 912 in a direction opposite of twisted area TA₁ toreturn cut width Wc to a similar orientation as shown in the cut patternin FIG. 9, which results in cut width Wc facing inward and outward alongat least a portion of first and second branch segments 911A, 911B ofstruts 912 and through crowns 913 of inflow portion 802.

In the embodiment of frame 810 shown in FIGS. 8 and 8A, inflow portion802 may be described as having a ring of equal or like sized and shapedcells C1 that are formed between respective portions of struts 912 andcrowns 913. In contrast to the symmetrical appearance of cells C1, C2 ofinflow portion 202 of frame 210 shown in FIG. 4A, cells C1 of inflowportion 802 of frame 810 shown in FIG. 8A appear to spiral clockwise.Although not intending to be bound by theory, the spiral appearance ofinflow portion 802 may be the result of all struts 912 having twistedareas TA₁ that twist or turn in a common or same direction fromvalve-retaining tubular section 804. In the embodiment shown in FIGS. 8and 8A, the twisted area TA₁ of each base segment 909 turns therespective strut 912 clockwise relative to inflow end 803 ofvalve-retaining portion 804 such that twisted area TA₁ may be consideredto have a right-hand twist. In another embodiment (not shown), thetwisted area TA₁ of each base segment 909 turns the respective strut 912counterclockwise relative to inflow end 803 of valve-retaining portion804 such that twisted area TA₁ may be considered to have a left-handtwist.

With reference to FIG. 8, first bend 816A of each s-shaped strut 912 hasan apex 822 that is longitudinally disposed at or near downstreamvalleys 914B of valve-retaining tubular portion 804. The increased depthof first bend 816A and the corresponding increased height of second bend816B, as compared to first and second bends 816A, 816B, respectively,are made possible by the longer length of inflow struts 912 relative toan axial length of valve-retaining tubular portion 804 as compared to alength of inflow struts 512 relative to an axial length ofvalve-retaining tubular portion 204. In another embodiment, apex 822 offirst bend 816A may be positioned at or near upstream valleys 914A ofvalve-retaining tubular portion 804, similar to the location of apex 422of first bend 416A as shown in FIGS. 4 and 7. In other embodiments inaccordance herewith, apex 822 of s-shaped struts 912 and apex 422 ofs-shaped struts 512 may be suitably disposed anywhere along the axiallength of valve-retaining tubular portions 204, 804, respectively, inorder to tailor the flexibility of the respective inlet portion 202, 802for a particular application.

The s-shaped struts 912 that form inflow portion 802 of frame 810 actsimilarly to cantilever beams when interacting with the anatomy of theheart as a supporting and sealing structure of a mitral valve prosthesisin accordance with embodiments hereof. During the pressure changes andcyclical contractions of the heart, the s-shaped struts 912 are able todeflect while maintaining an axial force against the atrial surface ofthe heart that is sufficient for sealing and the prevention ofparavalvular leakage between the frame and tissue surface. As well thecombination of twisted areas TA₁, TA₂, TA₃ and the s-shape of struts 912of inflow portion 802 permit the inflow area of mitral valve prosthesisin accordance with embodiments hereof to readily deflect, flex and/ormove during the cardiac cycle while also maintaining sufficient axialstiffness to provide sealing contact with the atrial surface thatsurrounds the implanted prosthesis. In addition, the twisted areas TA₁,TA₂, TA₃ of s-shaped struts 912 may reduce strain and improve thestructural integrity of frame 810, and more particularly the structuralintegrity of inflow portion 802 thereof. Another benefit of the designof inflow portion 802 of frame 810 is that it readily conforms to theD-shape of the mitral valve annulus by allowing deflection or movementin a radial direction D_(R) of struts 912 and the cells C1 definedthereby, as shown in FIGS. 10-12. FIG. 10 is a photographic image of animplanted mitral valve prosthesis having a frame 810 that shows howindividual struts 912 have radially deflected or moved afterimplantation to “lay down” a bit flatter and conform to the D-shape ofthe native mitral valve annulus. This anatomically conforming feature offrame 810 is more clearly depicted in FIGS. 11 and 12, with FIG. 11showing the deformation of inflow portion 802 of frame 810 afterimplantation and with FIG. 12 showing the post-implantation deformedinflow portion 802 of FIG. 11 (shown in cyan) transposed on apre-implantation inflow portion 802 of FIG. 8A (shown in red).

In order to transform between an initial compressed configuration andthe deployed configuration shown in the figures hereof, frames 210, 810in accordance with embodiments described herein are formed from aself-expanding material that has a mechanical memory to return to thedeployed configuration. Accordingly in accordance with embodimentshereof, frames 210, 810 may be made from stainless steel, apseudo-elastic metal such as a nickel titanium alloy or nitinol, or aso-called super alloy, which may have a base metal of nickel, cobalt,chromium, or other metal. Mechanical memory may be imparted to thetubular structure that forms frames 210, 810 by thermal treatment toachieve a spring temper in stainless steel, for example, or to set ashape memory in a susceptible metal alloy, such as nitinol. Mitral valveprosthesis in accordance with embodiments hereof may be delivered via atransapical implantation procedure or via a transatrial implantationprocedure. Suitable transapical and/or transatrial implantationprocedures that may be adapted for use with mitral valve prosthesisdescribed herein are disclosed in U.S. application Ser. No. 13/572,842filed Aug. 13, 2012 to Igor Kovalsky, U.S. Appl. Pub. No. 2011/0208297to Tuval et al., and U.S. Appl. Pub. No. 2012/0035722 to Tuval et al,each of which is incorporated by reference herein in its entirety.

In accordance with embodiments hereof, valve leaflets hereof, such asfirst and second valve leaflets 224A, 224B, may be made of or formedfrom a natural material obtained from, for example, heart valves, aorticroots, aortic walls, aortic leaflets, pericardial tissue, such aspericardial patches, bypass grafts, blood vessels, intestinal submucosaltissue, umbilical tissue and the like from humans or animals. Inaccordance with other embodiments hereof, synthetic materials suitablefor use as valve leaflets hereof, such as valve leaflets 224A, 224B,include DACRON® polyester commercially available from Invista NorthAmerica S.A.R.L. of Wilmington, Del., other cloth materials, nylonblends, polymeric materials, and vacuum deposition nitinol fabricatedmaterials. In an embodiment, valve leaflets hereof, such as valveleaflets 224A, 224B, can be made of an ultra-high molecular weightpolyethylene material commercially available under the trade designationDYNEEMA from Royal DSM of the Netherlands. With certain leafletmaterials, it may be desirable to coat one or both sides of the leafletwith a material that will prevent or minimize overgrowth. It is furtherdesirable that the leaflet material is durable and not subject tostretching, deforming, or fatigue.

In accordance with embodiments hereof, graft material 226 or portionsthereof may be a low-porosity woven fabric, such as polyester, DACRON®polyester, or polytetrafluoroethylene (PTFE), which creates a one-wayfluid passage when attached to frame 210. In an embodiment, graftmaterial 226 or portions thereof may be a looser knit or woven fabric,such as a polyester or PTFE knit, which can be utilized when it isdesired to provide a medium for tissue ingrowth and the ability for thefabric to stretch to conform to a curved surface. In another embodiment,polyester velour fabrics may alternatively be used for graft material226 or portions thereof, such as when it is desired to provide a mediumfor tissue ingrowth on one side and a smooth surface on the other side.These and other appropriate cardiovascular fabrics are commerciallyavailable from Bard Peripheral Vascular, Inc. of Tempe, Ariz., forexample. In another embodiment, graft material 226 or portions thereofmay be a natural material, such as pericardium or another membranoustissue.

In accordance with embodiments hereof, valve-retaining tubular portionsand support arms of frames disclosed herein, as well as the graftmaterial and tent-like structures that may be associated therewith, maybe modified without departing from the scope of the present invention inview of the disclosures of one or more of U.S. application Ser. No.13/736,460 filed Jan. 8, 2013 to Igor Kovalsky et al., U.S. Appl. No.61/822,616 filed May 13, 2013 to Kshitija Garde et al., and U.S.application Ser. No. 13/572,842 filed Aug. 13, 2012 to Igor Kovalsky,each of which is incorporated by reference herein in its entirety.

While various embodiments have been described above, it should beunderstood that they have been presented only as illustrations andexamples of the present invention, and not by way of limitation. It willbe apparent to persons skilled in the relevant art that various changesin form and detail can be made therein without departing from the spiritand scope of the invention. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the appendedclaims and their equivalents. It will also be understood that eachfeature of each embodiment discussed herein, and of each reference citedherein, can be used in combination with the features of any otherembodiment. All patents and publications discussed herein areincorporated by reference herein in their entirety.

What is claimed is:
 1. A mitral valve prosthesis comprising: a framehaving an inflow portion, a valve-retaining tubular portion and a pairof support arms, the inflow portion radially extending from a first endof the valve-retaining tubular portion and the pair of support armsbeing circumferentially spaced apart and extending from an opposingsecond end of the valve-retaining tubular portion, wherein the inflowportion is formed from a plurality of struts that outwardly extend fromthe first end of the valve-retaining tubular portion with adjacentstruts of the plurality of struts being joined, and wherein each strutof the plurality of struts has a substantially s-shaped profile and atleast one twisted area.
 2. The mitral valve prosthesis of claim 1,wherein adjacent struts of the plurality of struts are joined byrespective crowns.
 3. The mitral valve prosthesis of claim 2, whereinadjacent crowns are not directly attached to each other.
 4. The mitralvalve prosthesis of claim 1, wherein each strut has a base segmentjoined to the valve-retaining tubular portion and wherein the basesegment has a twisted area.
 5. The mitral valve prosthesis of claim 4,wherein twisted areas of the base segments of the plurality of strutsare twisted in the same direction.
 6. The mitral valve prosthesis ofclaim 4, wherein the base segment of each strut radially extends from arespective valley at the first end of the valve-retaining tubularportion.
 7. The mitral valve prosthesis of claim 4, wherein a pair ofbase segments radially extends from every other valley at the first endof the valve-retaining tubular portion.
 8. The mitral valve prosthesisof claim 7, wherein the twisted area of a first base segment of eachpair of base segments twists in an opposite direction from the twistedarea of a second base segment of each pair of base segments.
 9. Themitral valve prosthesis of claim 4, wherein each strut has first andsecond branch segments that diverge from the base segment and whereineach of the first and second branch segments has a respective twistedarea.
 10. The mitral valve prosthesis of claim 9, wherein first andsecond branch segments of adjacent struts are joined to each other by arespective crown.
 11. The mitral valve prosthesis of claim 1, whereineach strut has a first bend and an opposing second bend that form thesubstantially s-shaped profile thereof.
 12. The mitral valve prosthesisof claim 11, wherein one of the first and second bends of each strut hasan apex that is longitudinally disposed at or near downstream valleys ofthe valve-retaining tubular portion.
 13. A mitral valve prosthesiscomprising: a frame having an inflow portion, and a valve-retainingtubular portion, wherein in a deployed configuration the inflow portionof the frame radially extends from a first end of the valve-retainingtubular portion, and wherein the inflow portion of the frame iscomprised of a plurality of struts with each strut forming asubstantially s-shaped profile and having at least one twisted area whenradially extending from the first end of the valve-retaining tubularportion in the deployed configuration.
 14. The mitral valve prosthesisof claim 13, wherein adjacent struts of the plurality of struts arejoined by respective crowns.
 15. The mitral valve prosthesis of claim14, wherein adjacent crowns are not directly attached to each other. 16.The mitral valve prosthesis of claim 13, wherein each strut is Y-shapedhaving a base segment and first and second branch segments that divergefrom the base segment.
 17. The mitral valve prosthesis of claim 16,wherein the base segment of each strut is joined to the valve-retainingtubular portion and wherein the base segment has a twisted area.
 18. Themitral valve prosthesis of claim 17, wherein each of the first andsecond branch segments of each strut has a respective twisted area. 19.The mitral valve prosthesis of claim 13, wherein each strut has a firstbend and an opposing second bend that form the substantially s-shapedprofile thereof.
 20. The mitral valve prosthesis of claim 19, whereinone of the first and second bends of each strut has an apex that islongitudinally disposed at or near downstream valleys of thevalve-retaining tubular portion.